Continuity mistake: Towards the end while Django is taking the horse from the cart with the slave cage, the sun changes between shots.
Continuity mistake: After the Mandingo fight when Calvin asks Django what makes him such a Mandingo expert, Calvin's bodyguard - Butch is seen hitting the cue ball on the pool table to the right corner. After Django smartly responds "I'm curious what makes you so curious." and Butch says "what did you say, boy?" the cue ball returns back to its original position on the table.
Continuity mistake: When Django is shown looking at various hats, he tries on a top hat. It is level on the stand when he picks it up, and when he puts it back it is now at a noticeable slant. After some dialogue the shot comes back to include the hats and the top hat has become perfectly level once again.
Continuity mistake: At the beginning, Jamie Foxx's scar on his forehead comes and goes as the white man picks him out of the chain gang.
Continuity mistake: Ace Speck's hat changes positions while he lies dead and Django and Schultz move around the place.
Answer: Django and Schultz killed some of Big Daddy's farmhands, and he wasn't going to let a freed slave kill some of his workers. Schultz knew Big Daddy would come after them for what they did. Plus Django would never let go of a chance to kill a slave owner who was trying to kill him.